Thermal timing switch apparatus



Aug. 10, 1948. F. w. HoTTENRoTH, JR 2,446,831

' THERMAL TIMING SWITCH APPARATUS Filed Feb.v 12, 1944 2 sheets-sheet 1 Pjgl. 24 ha 25 Pig. 2.

by )y His ttorney.

Aug- 10, 1948- F. w. HOTTENROTH, JR 2,446,831

THERMAL TIMING SWITCH APPARATUS Filed Feb. 12, 1944 2 Sheets-Sheet 2 Inventor Frederick W. Hottenroth Jn? Patented Aug. 10, 1948- THERMAL TIMING SWITCH APPARATUS Frederick W. Hottenroth, Jr., Schenectady, N. Y.,

assigner to General Electric Company, a corporation of New York Application February 12, 1944, Serial No. 522,117

(Cl. 20G-122) 1o claims.

My invention relates to thermal timing apparatus, and particularly to ambient temperature compensated thermal timing devices which may be adjusted to operate either as impulse thermal timers or variable time recycling timers.

In thermally timing an operation, it has been common heretofore to energize a thermal responsive member to effect a desired control function after a timed interval and to maintain the thermal responsive member energized so long as the control function is exercised. Such an arrangement has the obvious disadvantage that, if it is desired to retime an interval immediately upon discontinuance of a control function, the thermal responsive member will not have sufficient-time to return to its normal cooled position, and the desired timing operation will not be properly effected. To avoid such shortening or omission of a timing operation, it is desirable to use an impulse-type timer which, after timing an interval and initiatingV a desired controlled operation, automatically returns to its initial position without interrupting the continuation of the controlled operation. Such a timer positively ensures proper timing of the desired interval during each operation of the controlled ap-A paratus.

Accordingly, it is a general object of my invention to provide a, new and improved thermal timing apparatus which is inexpensive and easily assembled as well as eitlcient and reliable in operation.

It is a further object of my invention to pro-l vide a new and improved thermal timing apparatus which is compensated for changes in ambient temperature.

It is a sti-ll further object of my invention to provide a new and improved thermal timing apparatus of the impulse type which effects a locking-in operation of the controlled apparatus and automatically returns to its normal position.

It is still another object of my invention to provide a thermal impulse timer which requires resetting operation after each interval timing operation thereby to ensure proper interval timing. I

sive members, such as deformable bimetallic elements or the like. The movable switch member is :arrangedy by its movement to control a snapacting switch, the actuating member of whichv exhibits a definite differential between the positions at which it effects-opening and reclosing of any pair of cooperating switch contacts. Suitable biasing means are provided for adjusting the normal position of the movable switch member. Thus, when the switch member is adjusted so that its normal position falls within the posil tional differential of the switch, the timer may then be effected by operating the switch member in the opposite direction to reset the switch and allowing it again to resume its normal position in preparation for the timing of another interval.' E

By so adjusting the normal position ofthe movable switch member that it is at or beyond one if the limits of positional diiferential of the switch, the timer may be used as a recycling timer in a manner to be more fully described hereinafter. The nature of my invention will be more fully understood and its objects and advantages further appreciated by referring now to the following detailed specification taken in conjunction with they accompanying drawings in which Fig. 1 is a plan view of a thermal timing apparatus embodying my invention; Fig. 2 is a cross-sectional view taken along the 'line 2-`2 of Fig. 1- looking in the direction of the arrows; Fig. 3 is a cross-' sectional View taken along the line 3-3 of Fig. 1 looking in the direction of the arrows; Figs. 4, 5', 6 and 7 are schematic circuit diagrams illustrating various representative timing circuits including the timing apparatus shown at Figs. 1Q 2 and 3; and Fig. 8 is a side elevation of a snapacting switch of a type applicable in connection It is still another object of my invention t0 with my invention. l I

Referring now to the drawings, and particui larly to Figs. 1, 2 and 3, the thermal timing apparatus therein illustrated to show` one form which my invention may take comprises a casing I0, preferably formed of a suitable molded electric insulating material and provided with substantially perpendicular internal dividing walls II, I2 and I3 separating the casing into a pair of adjacent upper compartments Il and I5 vand a lower compartment I6.

adjacent ends of the walls Il, I2 and I3, where,

the walls are spaced apart to provide space for 'a movable switch member which is pivotally mounted uponva centrally located pivot pin il. The pin il is supported in a U-shaped yoke it xedly mounted upon the casing it, as best shown at Fig. 3. The movable switch member comprises a U-shaped saddle i9 rotatably mounted upon the pivot pin il! and having attached thereto an extending switch arm to. Theimovable switch arm 2o extends trom the saddle it.

into the compartment te. The compartment i@ vconstitutes a switch compartment.

Also attached to the movable switch member at the bight of the U-shaped saddle it and exv tending in the opposite direction from the switch arm 2o and into the compartments itl and it respectively. are a pair of dat thermal responsive bimetal elements 2i and 22. En the form of the invention shown in the drawing, the bimetal elements 2l and t2 are formed of a single strip of bimetallicmaterial bent around a suitable seat formed by the base of the movable saddle iti and riveted, or otherwise suitably attached, to the saddle. I wish to have it understood, however. that my invention is not limited to this particular manner of mounting the blmetallic elements, but that, if desired, the thermal responsive ele-I ments 2i and 22 may be formed of separate strips ofbimetallic material and separately at-1 tached to the movable switch member.

The thermal responsive bimetal elements 2i and 22 extend from the saddle i@ through the compartments ill and l5 and into engagement with a pair of abutments 2li and 2b formed upon the casing i@ adjacent the free ends of the elements 2l and 22, The bimetal elements 2l and 22 are initially slightly stressed against the abutments 2li and 25 and are arranged to be heated by electric heating elements 2b and fil, respectively, mounted within the compartments it and it in heat conductive relation to the elements 2i and 22. The compartments it and i5 serve 'thermally to isolate the heater it and bimetalllc strip 2i from the heater 2l and bimetallic strip 22. The small passages connecting the compartments I'4 and i5 with the compartment l@ are suiciently large to accommodate the bimetallic strips 2i and 22, but are not suiciently large to provide appreciable interchange of heat between the compartments.

Within the switch compartment it and in operative relation with respect to the movable switch member 2i, is positioned a snap-acting overcenter elect-ric switch 3@ having anactuating member 35 and two pairs oi electric switch contact terminals it and 3l'. For convenience, the switch contacty terminals il@ may be wired to external binding posts 3b. Preferably, the snapacting switch 3@ is of the type described and claimed in Patent 2,332,911 and shown at Fig. 8, issued to George M. Hausler on October 26, 1943. As described in that patent and shown at Fig. 8, thisl switch is an overcenter snap-acting switch having a bridging contact member arranged alternatively to bridge the stationary contacts oon- As described in the above-mentioned patent to Hausler, the switch actuating member 35 may be normally biased to one position. According to the present invention,l the switch 30 is of such a type that the actuating member 35 is normally biased toward and into engagement with the movable switch arm 20, so that it tends to rotate the movable switch member in a counterclockwise direction, as viewed at Fig. l. For the purpose ci adjusting the normal position of the movable switch arml 2li, a compression spring til is positioned between the switch arm and the side of lthe casingvlil. Preferably, a nut tl and an adswitch arm 2@ takes up a position'intermediate its two spaced-apart switch actuating positions. That is, the normal position of the switch arm 2t, when neither bimetallic element 2i or 22 is heated, is within and preferably midway within the positional differential of the snap-acting l switch to. Referring now to Fig. e, where ll have nected to the pairs of terminals 3d or 3l. The 65 switch actuating member 35 is reciprocable to move the bridging contact member overcenter in both directions of movement, so that the dead shown my timing apparatus connected as an impulse-type timer, this condition is indicatedby the dotted lines d5 and i6 which indicate, re-

spectively, the positions of the actuating member lt5 for opening and reclosing the circuit through the switch terminals Eil?. The actuating member 35 is shown in a normal position C midway between the positions l5 and llt.

At Fig. i I have also shown the electric heating elements 2S and 2l connected to a suitable source lofvelectrio current supply through a pair of line conductors d?. The heater 2d `is connected to the conductors il through the contact terminals @l of the switch di). The electric heating element r2l is connected to the line conductors di through a manually operable push button iid. I have also indicated at Fig. d that, when heated, the bimetallic elements 2i and 22 are so deformed that their free ends tend to move toward each other and away from their respective casing abutments 241 and 25.

In operation, the impulse timing apparatus illustrated at Fig. d functions in the following manner. Let it rst be assumed that the apparatus is in the normal deenergized position, as shown, and that the circuit between the contact terminals 3i is closed. Ii now electric energy is suppliedto the line conductors dill, only the electric heating element 26 will be energized .and the free end of the bimetallic element 2i will tend to move away from the abutment 2t and toward the free end of the bimetallic element 22. However, because of the fact that the bimetallic elements 2i and 22' are initially stressed when in their unheated condition, heating of the `bimetallic element 2i does not 'actuallyv remove its free end from the abutment 24, but lmerely releases some of the stress in the element.` This is equivalent to increasing the stress upon the bimetallic element 22 and results in rotating the movable switch bmember in a counterclockwise direction. As the movable switch arm 20 moves counterclockwise, as viewed at Fig. 4, the actuating member 35 of the snap-acting switch 30 follows under the inuence of its own biasing spring until it reaches the position t5 Where the circuit between the contact terminals 3l is broken. Thus, the electric heating element 28 is deenergized, so that the movable switch arm. 2@

C. In returning to this position, however; the switch Il is not again actuated by reason ot the fact that reclosing of the circuit between the contactterminalsll doesnottakeplaceuntilthe actuating member Il reaches the position 4l. It will now be evident that the switch contacts connectedtothepairoiterminalsrmaybeused to eil'ectany desired control function. and that the timing device controls these contacts through a self-terminated impulse and eectually locks the contacts in position to maintain a controlled operation despite the fact that the movable switch' member retin'ns to its normal position.

I! now it is desired to retime an interval by again closing the circuit between the contact terminals lt, it is first necessary to reset the timing apparatus by depressing the push button 4l to energize the electric heating element 21. When the electric heating element 21 is energized, the movable switch arm 2li is rotated in a clockwise direction, as viewed at Fig. 1, until the switch actuating member I5 reaches the position Il to reset the switch with the contact terminals 31 bridged. I'he pushbutton 48 may then be re- )leased to allow the movable switch arm 20 to return to its normal position. The cycle o! operation may now be repeated to reclose the circuit between the contact terminals 38. It will ot course be appreciated that preferably suitable interlocking means is provided to prevent reali-v plication of power to the controlled apparatus until the timing apparatus is reset with the circuit between the contact terminals II open.

By way of illustration of its many applications, the arrangement described above in connection with Fig. 4 has been found useful in timing the operation of a pump for maintaining circulation of the lubricating oil in an internal combustion engine for a predetermined period alter the engine is stopped. For this purpose, the heater 2t is automatically energized upon cessation of engine operation and deenergized at its own interlock contacts in the manner described. The pump is deenergized when the switch ll is actuated and, since the heater 26 is also deenergized at this time without reversing the switch operation, it is unnecessary to maintain the thermal element heated in order to prevent further pump operation. In order to reset the impulse timer, any desired suitable arrangement may be made automatically to energize the heater 21 for a short time in response to engine starting. If desired, of course, another interlock contact on the switch 30 may be used to deenergize the heater 21 as soon as the switch 2li is reset.

At Fig. 5, I have illustrated another embodiment of my invention in which the disposition of the bimetallic elements 2| and 22 is reversed, so that the free ends of these elements tend to move toward the abutments 24 and 25, respectively; and away-from each other as heat is applied to the elements. In order to understand this embodiment of the invention, it may be noted that the bimetallic elements 2| and 22 may be positioned for deilection in either direction upon the application oi heat thereto, it being only necessary that they be connected in opposition to each other. Thus, when heat is applied to the bimetal element 2| of Fig. 5 by the electric heating element 2 B, the stress in the bimetal element 2| is increased and the movable switch arm 20 rotated in a clockwise direction, as viewed at Fig. 5. This operation will be understood from the fact that an increase in stress of the bimetal element 2| is 'amaai ultimately returns to its noi-mal eenwposition' equivalent totvplyins to the free end of the element 2| a force tending to move the free end toward the right. as viewed at Fig. 5. It will be noted from Fig. 5 that the electric heating element 2l is connected for' control to the contact terminals Il of the switch Il rather than to the contact terminals 21. Since the circuitbetween the terminals 3l is open when that between the terminals 81 is closed, it will be understood that the open and closed positions l5 and I6, respectively, oi' the switch actuating member 35 are reversed-with respect to those shown at Fig. 4, while the positional diil'erential therebetween is the same. As at Fig. 4, the movable switch arm 20 is normally positioned at C midway between its opening and closing positions for the pair of contacts connected to the terminals 38.

The operation oi the arrangement shown in Fig. 5 will be understood from the previous description of the operation of the arrangement oi' Fig. 4. Briey, it may be noted that. if it is assumed that initially the contact terminals 36 are connected by the bridging contact of the switch 30 and heat is supplied to the bimetallic element 2| through the electric heating element 26, the movable switch arm 2l will be rotated in a clockwise direction, as viewed at Fig. 5, until the actuating member 35 reaches the position 45 to open the circuit between the contact terminals 36. When the circuit between the terminals 3.8 is opened, the electric heating resistor 26 is deenergized and the movable switch arm 20 auto-V matically returns to its normal central position without further aecting the switch contacts. In order to reset the switch. the electric heating element 21 is briefly energized to rotate the movable switch arm 20 in a counterclockwise direction to the position Il whereupon the element 21 may be deenergized and the movable switch member allowed to return to its normal central position.

Referring now to Fig. 6 I have illustratedl schematically therein a circuit arrangement for utilizing my new and improved thermal timing apparatus as an automatic recycling timer with an adjustable periodicity. This form of the invention is characterized principally by the'fact that the spring 4l of the timing device is so adjusted that the movable switch arm 20 is normally in the contact closing position for the interlock contact terminals I1 connected in series circuit relation with the electric heating element 26.' 'I'hat is, with respect to the heater control contact of the switch 3l the normal position of the switch arm 2|! is adjusted to the closing limit of the positional differential of the switch. At Fig. 6, I have also shown a variable resistor 50 connected in series circuit relation with the electric heating element 21 to render the heating element 21 of less heatingcapacity than the'element 26 and also to vary the degree of inequality between the heating elements 25 and 21 while maintaining the element 21 always of the smaller capacity. Attention is also directed to the fact that at Fig. 6 it has been assumed that the blmetallic elements 2| and 22 are so disposed that when heated their free ends tend to move toward each other and away from the casing abutments 24 and 25, respectively.

In operation, when energy is supplied to the line conductors I1 of Fig. 6, both heating elements 2| and 22 are simultaneously energized. The heating element 2i, however, being of greater capacity than the element 21, heats the bimetallic l element 2| yto a greaterextent than the bimetallic arm 2c in a counterclockwise direction, as viewed at Fig. 6, ,thereby to move the switch actuating member E35 from the closed position lit to the open position 45. At the position ttl, the interlock contacts connected to the switch terminals 31 are open-circuited and the heating element 2t is deenergized. Energization of the heating element 27, however, is not interrupted, so that the blmetallic element 22 continues to receive heat as the element 2i cools. Under these conditions, the movable switch arm 201is rotated in a clockwise direction, as viewed at Fig. 6, from the position d back. to the position 46, thereby to reclose the interlock contacts 3l and to reenergize the heating element 26. It will now be evident that the foregoing cycle of operation will be repeated indefinitely and with a periodicity depending upon the diierence in the heating capacities of the elements 28 and 21. Since the heating capacity of the element 21 is controlled by the Variable resistor 5U, it will be evident that the resistor 50 provides a means for adjusting the periodicity of recycling operation.

It will be understood from the foregoing explanation of Figs. 4 and 5 that if the bimetallic elements 2i and 22 of Fig. 6 are reversed so that their free ends tend to move apart and toward the casing abutments 24 and 25 when heat is applied thereto, the directions of rotation of the movable switch arm 20 will be reversed. In this event, recycling operation may be effected in the same manner as described in connection with Fig. 6 if the electric heating element 26 is connected for control to the switch terminals 36 andv the initial position of the switch arm 20 is adjusted to the closing limit of positional differential for the contact terminals 36. Operation oi this arrangement will be understood from the foregoing explanation of the operation of Fig. 6.

Referring now to Fig. 7, I have illustrated another recycling timer apparatus similar to that of Fig. 6, but in which the heater controlling contacts of the switch 3@ are maintained normally open with the bimetallic elements 2i and 22 disposed inthe same manner as in Fig. 6. The embodiment of Fig. 7 may be attained by adjusting the switch actuating member` 35 to the opposite limit of the switch positional difierential and leaving the heater 2t connected for control to the contact terminals 3l. With such an arrangement, illustrated at Fig. "l, it Will be observed that when electric energy is supplied to the conductors t7 only the heating element 2l is initially energized. Energizatio'n of only the element 2l eiects the :clockwise rotation of the switch arm 2li, as viewed at Figb 7, from the position 45 to the position L16, thereby to close the circuit of the electric heating element 2S. When the heating element 26 of greater capacity than the element 2l is energized, the net elect of the heat applied to the bimetallic elements 2| and 22 will rotate the movable switch arm 2d in a counterclockwise direction, as viewed at Fig. 1, thereby to move the switch actuating member 35 from the position 46 to the position i5 and to reopen the circuit of the heating element 26. This recycling operation will continue indefinitely at a periodicity determined by the adjustments 24 and 25, respectively, recycling opera-- tion may be effected by connecting the heating element for control to the contact terminals 36 and resetting the normal position of the switch arm 2li to the opening limit of differential for the switch contacts connected to the terminals 36.

In view of the foregoing, it will now be evident that my invention lprovides a new and novel thermal timing apparatus which is simple in construction, reliable and rugged in operation, and extremely versatile in application.

While I have illustrated only certain preferred embodiments of msi-invention by way of illustration, many modifications will occur to those skilled in the art and I therefore Wish to have it understood that I intend in the appended claims to cover all such modifications as iall within the true spirit and scope of my invention.

What I claim as new and desire to secure 'by Letters Patent of the United States is:

1. An ambient temperature compensated thermal timing apparatus comprising a movable' switch member, a pair of thermal responsive members connected together in opposing relation and to said switch member jointly to control said switch member, separate electric heating means of unequal/capacity disposed in heat conductive relation with said thermal responsive members, and a snap acting switch by said switch member and arranged to control only one of said electric heating means, said switch having a predetermined positional diderential between circuit opening and circuit closing positions and being so positioned that said switch member normally lies at one limit of said differential. 2. An ambient temperature compensated thermal timing apparatus comprising a base, a pivotally mounted movable switch member, a pair of thermally deformable arms mounted upon said switch member and extending in substantially parallel spaced `relation into abutting engagement with said base, said arms being disposed ior deformation in opposite directions upon like changes in temperature, separate electric heating means for supplying heat to said arms, anda snap acting switch actuated by said switch member and arranged to control one only of said electric heating means, said switch having a predetermined positional diierential between circuit opening and circuit closing positions and being so positioned that said switch member operates within said dierential.

3. An ambient temperature compensated thermal timing apparatus comprising a base having a plurality of substantially thermally isolated compartments, a movable switch member vpivotally mounted upon said base, a pair of thermally deformable arms carried by said switch member and extending in substantially parallel spaced relation into separate compartments of said base and into abutting engagement with said base, said arms being disposed for deformation in opposite directions upon like changes in temperature, separate electric heating means disposed in said compartments to supply heat to said arms, and a pair of cooperating switch con"- tacts actuated by said switch member to control one of said electric heating means.

4. An ambient temperature compensated thermal timing apparatus comprising a base having a plurality of substantially thermally isolated compartments therein, a movable switch member pivotally mounted upon said base, a pair of thermally deformable arms carried by said switch member and extending through separate compartments into abutting engagement with said base, said arms being disposed for deformation in opposite directions upon like changes in temperature. separate electric heating means in said compartments in heat conductive relation with said arms, an electric switch contact member actuated by said movable switch member and having a predetermined positional differential between contact opening and contact closing positions, said switch contact mem- I ber being connected to control the energization oi' one of said electric heating means, and means ior adjusting the normal position oi said switch member throughout the limits of said positional differential.

5. A thermal impulse timer comprising a pair of thermal responsive members connected together in opposing relation, separate electric heating means disposed in heat conductive relation with said thermal responsive members, a switch member movable under the joint control of said thermal responsive members, a pair of cooperating switch contacts relatively movable by said switch member and connected to control the energization of only one o! said electric heating means, said switch member having a predetermined positional differential between contact opening and contact closing positions and being normally positioned intermediate said opening and closing positions, and means for energizing said one electric heating means to time an interval, said other electric heating means when energized resetting said switch contacts.

6. A thermal impulse timer comprising a movable switch member, a -pair of thermal responsive members connected in opposing relation jointly to control said movable switch member, separate heating means disposed in heat conductive relation with said thermal responsive members, a pair of snap-acting switch contacts actuated by said switch member and providing a predetermined positional diil'erential between contact opening and contact closing positions of said switch member, said contacts being connected to deenergize one of said electric heating means when said switch member is moved a predetermined amount by the associated thermal y responsive member, means for normally main-l tainingsaid switch member in a position intermediate said opening and closing positions, and manually operable means for energizing the other oi' said electric heating means to reset said switch contacts.

7. A thermal impulse timer comprising a base having a plurality o! substantially thermally isolated compartments therein, a movable switch member pivotally mounted upon said base, a pair o! thermally deformable bimetallic members mounted upon said switch member in cantilever fashion and extending through separate compartments into abutting engagement with said base, said bimetallic members being disposed for deformation in opposite directions upon like changes in temperature, separate electric heating means disposed in heat conductive relation with said bimetallic members, an overcenter snapacting electric switch contact actuated by said switch member and providing a predetermined positional diiierential between contact opening and contact closing positions of said switch member, said switch contact being connected to deenergize one of said electric heating means when said switch member is moved a predetermined amount by the associated bimetallic member, and means for normally maintaining said switch 10 member in a position intermediate said opening and closing positions.

8. A recycling thermal timing apparatus comprising a pair oi thermal responsive members connected togetherin opposing relation, separate electric heating means of unequal capacity disposed in heat conductive relation with said thermal responsive members, a switch member movable under the joint control of said thermal responsive members, a snap acting switch actuated by said switch member and arranged to control the energization of only said electric .heating means oi?- greater capacity, said snap acting switch having a predetermined positional diil'erential between circuit opening and circuit closing positions and being so positioned that said switch member is normally positioned at one limit of said diierential.

9. A recycling thermal timing apparatus comprising a movable switch member, a pair o! thermal responsive members connected to said switch member in opposing relation, separate electric heating means oi' unequal capacity disposed in heat conductive relation with said thermal responsive members, a pair of cooperating switch contacts movable in opposite direction with a snap-action at spaced-apart switch actuating positions of said switch member and connected to control the energization of said electric heating means of greater capacity, and means for maintaining said switch member normally in one oi' said switch actuating positions.

10. A recycling thermal timing apparatus comprising a base having -a plurality of substantially thermally isolated compartments therein, a movable switch member pivotally mounted upon said base, a pair oi' thermally deformable bimetallic members mounted upon said switch member and extending through separate compartments of said base into abutting engagement with said base, said bimetallic members being disposed for deformation in opposite directions upon like changes in temperature, separate electric heating means of unequal capacity disposed in said compartment in heat conductive relation with said bimetallic members, an electric switch contact member actuated 'by said movable switch member and having a predetermined positional differential between contact opening and contact closing positions, said switch contact member being connected to deenergize said electric heating means of greater capacity whenl said switch member is moved afpredetermined amount under the predominant iniluence oi the associated bimetallic member, and means for maintaining said switch member in a normal position at one limit of said positional differential.

FREDERICK W. HOTI'ENRUII-I. Ja.

REFERENCES crran The following references are oi record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 1,694,709 Lowenstein Sept. 18, 1928 1,719,089 Starr July 2. 1929 1,734,095 Mancib Nov. 5, 1929 1,867,380 Runyon July 12, 1932 2,002,467 Blodgett May 21, 1935 2,195,947 Uhlrig Apr. 2, 1940 2,238,219 Finerman Apr. 15, 1941 2,275,917 Newell Mar. 10, 1942 2,285,877 Myers June 9, 1942 

